1. Chapter 12 Chapter 12 The Global Cycles of Nitrogen and Phosphorus Copyright © 2013 Elsevier Inc. All rights reserved.

2. FIGURE 12.1 Microbial transformations in the nitrogen cycle (DNRA = Dissimilatory Nitrate Reduction to Ammonium). Source: Modified from Wollast (1981). 2

3. Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 12.2 The global nitrogen cycle. Each flux is shown in units of 10 12 g N/yr. Values as derived in the text. See also Table 12.3. 3

4. Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 12.3 Deposition of NO y on Earth's surface. All values are mg N m - 2 yr -1. Source: From Dentener et al. (2006). 4

5. Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 12.4 The 200-year record of nitrate in layers of the Greenland ice pack and the annual production of nitric oxides by fossil fuel combustion in the United States. Source: Modified from Mayewski et al. (1990). 5

6. Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 12.5 The production history of nitrogen fertilizer. Source: From Robertson et al. (2009). Used with permission of the Annual Review. 6

7. Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 12.6 Nitrous oxide measurements from ice-core samples in Antarctica. Source: From Flückiger et al. (2002). 7

8. Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 12.7 The global phosphorus cycle. Each flux is shown in units of 10 12 g P/yr. Values for P production and reserves are taken from the U.S. Geological Survey. Estimate for sediments is from Van Cappellen et al. (1996), and estimates for other pools and flux are derived from the text. 8

9. Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 12.8 Net primary production versus nitrogen inputs to terrestrial, aquatic, and marine ecosystems. Net primary production increases in direct response to added nitrogen up to inputs of about 10 g N m -2 yr -1 (100 kg/ha). Inputs in excess of that level are rarely found in natural ecosystems, but are seen in polluted environments and agricultural soils Source: Modified, with permission from Princeton University Press, from Levin (1989). 9

10. Copyright © 2013 Elsevier Inc. All rights reserved. TABLE 12.1 A Global Budget for Atmosphere NO X (values are Tg N (10 12 gN)/yr as NO 10

11. Copyright © 2013 Elsevier Inc. All rights reserved. TABLE 12.2 A Global Budget for Atmospheric Ammonia 11

12. Copyright © 2013 Elsevier Inc. All rights reserved. TABLE 12.3 Mass Balance for Nitrogen on the Earth’s Land Surface 12

13. Copyright © 2013 Elsevier Inc. All rights reserved. TABLE 12.4 A Global Estimate of Denitrification of Nitrogenon or Applied to Land 13

14. Copyright © 2013 Elsevier Inc. All rights reserved. TABLE 12.5 A Global Budget for Nitrous Oxide (N 2 O) in the Atmosphere (all values are Tg N/yr (10 12 g/yr) nitrogen, as N 2 O) 14